"With respect to these [safety] enhancements, we have particular concern about the potential requirement to install "filtered vents" for certain boiling water reactors which we understand to be significant, capital-intensive structures. As instructed by the Commission, the NRC staff has proposed four potential options but urged the Commission to choose "Option 3." Under this option, the Commission would issue an order requiring the installation of fintered vents rather than pursuing a performance-based process."

Now, the Nuclear Regulatory Commission will "study options" and won't make the final rule till March 2017. The Commission's thinking as you can read in the article below take the House Energy and Commerce Committee's thinking extremely seriously.

From Power News (3/21/2013; links are in the original, emphasis is mine):

NRC Delays Action on Vent Plan, Directs Staff to Study Options

The Nuclear Regulatory Commission (NRC) on Tuesday delayed approving a recommendation made by technical staff that calls for upgrades or replacements of "hardened" venting systems at the nation's 31 Mark I and Mark II boiling water reactors (BWRs), giving staff a year instead to assess other options and produce a "technical evaluation" on the proposal.

The NRC commissioners directed staff to follow a two-track approach for further improvements to systems for safely venting pressure during potential accidents at the reactors, in response to the Fukushima accident in March 2011. It gave the staff 60 days to finalize a March 2012 order, which will require vents to handle elevated pressures, temperatures, and radiation from a damaged reactor. The order will also ensure plant personnel can operate vents safely under these accident conditions.

It also gave the staff a year to produce a technical evaluation to support rulemaking on filtering, gathering more public input as it completes its analysis. Directing the staff to consider both the use of a filter to be placed on the vent, as well as a more performance-based approach using existing systems to achieve a similar reduction in radioactive release during an accident, the commission said the draft rule and final rule must be ready by March 2017.

A vent generally refers to a pipe connected to the primary containment of a nuclear power plant and leading to the plant’s exhaust stack. It is designed to allow gases inside the containment to be removed. “The major problem at Fukushima was getting the containment vents open,” said Doug True, president of ERIN Engineering and Research told Nuclear Insight last fall. “Significant delays in the decision to open the vents, combined with the Japanese decision-making process and difficulties in opening the vent valves, delayed the venting action, which in turn led to hydrogen explosions.”

The NRC's decision was widely viewed as a victory for the nuclear industry. The NRC has estimated that filtered vents could cost up to $15 million, but other estimates put costs of equipment at $30 million or more.

But media reports accusing the nuclear energy industry of opposing the installation of filtered vents on Mark I and II BWRs are incorrect, say Jason Zorn, assistant general counsel, and Steven Kraft, senior technical advisor at the Nuclear Energy Institute (NEI ). The issue is a technical one. "In the extremely unlikely event that an accident progresses to the point of the fuel melting through the reactor vessel onto the containment floor, it is imperative that water be injected into containment to cool the fuel debris on the floor," they say. "If not, radiation releases will occur from numerous locations in the containment building and bypass the vent. If the vent is bypassed, it doesn’t help if there is a filter on the vent, because it, too, will be bypassed."

Filtering strategies based on the individual plant evaluations could result in the installation of a vent filter, "if that’s what makes sense for a given plant," they said.

Sources: POWERnews, NRC, Nuclear Insight, NEI

“Significant delays in the decision to open the vents, combined with the Japanese decision-making process and difficulties in opening the vent valves, delayed the venting action, which in turn led to hydrogen explosions"?

The vents couldn't be opened for a long time because there was no power. There are experts and engineers who have proposed that instead of delay in venting leading to hydrogen explosion, venting may actually have caused hydrogen explosions in Reactors 1 and 3 because of the peculiar structure of the exhausts stacks and power loss. Instead of leaving via the exhaust stack, vented hydrogen gas came back inside the reactor building, they say.

Water under the bridge at this point, except that inaccurate understanding of the Fukushima I Nuclear Power Plant accident is being used as excuse.

An approach to designing and operating nuclear facilities that prevents and mitigates accidents that release radiation or hazardous materials. The key is creating multiple independent and redundant layers of defense to compensate for potential human and mechanical failures so that no single layer, no matter how robust, is exclusively relied upon. Defense-in-depth includes the use of access controls, physical barriers, redundant and diverse key safety functions, and emergency response measures. For further information, see Speech No. S-04-009 (PDF), "The Very Best-Laid Plans (the NRC's Defense-in Depth Philosophy)."

12
comments:

Anonymous
said...

J. Zorn's explanation doesn't really make sense: to be able to easily inject water in the case of a very severe core melt in order to avoid melt-through, you need a means to safely decrease the inner pressure by removing the accumulated hydrogen.For all practical purposes, this means venting through a filtered system, so that exposure of the operators and emergency crew is low. One can see the impediment the on-site radioactivity was in Fukushima after the explosions and the unfiltered venting! Filters also come with rupture disks, avoiding overpressure and thus uncontrolled releases on the confinement even if you are not able to activate the venting valves for some reason.So filters are great for accident management. Of course, they're also great for the surrounding land…

@Anon 3:53PM. The main argument made by Sherrell Greene against filters is that once activated, they cannot be closed. This is mixing thing up, and concerns the rupture disk, NOT the filter.Modern European designs will have valves in parallel with the rupture disk:1) You CAN vent and close the filtered vent manually, with the valves, as long as you have control of the plant.2) Uncontrolled venting via the rupture disk will only happen if pressure rises to a point where containment integrity is threatened, i.e. if somehow the operators completely lose control of the plant and cannot operate the valves. Note this is an extreme case, because the valves are designed to be manually operated from special shielded spots.The philosophy is that passive venting will always be better than having the containment fail in an unpredictable way (see Fuku I-1, apparently H2 in the building…).

In any case, be it active (valves) or passive venting (rupture disk), you're obviously better off with a filter! The whole thing is basically a no-brainer, as all this evaluation and the detailed design stuff (valve + rupture disk layout, explosion shields, radionucleide absorption, thermal requirements, etc.), was carried out in Europe 20-30 years ago…

Exactly, at Fukushima they did not have "not to vent" as a choice.However, even better than filters, you are better off with a non-nuclear powerplant; anything that does not require a caveat like "as long as you have control of the plant".

@Above: "better off with a non-nuclear powerplant"?Maybe not:http://pubs.acs.org/doi/abs/10.1021/es3051197"Prevented mortality and greenhouse gas emissions from historical and projected nuclear power"Pushker A. Kharecha and James E HansenEnviron. Sci. Technol., 2013"Using historical production data, we calculate that global nuclear power has prevented about 1.84 million air pollution-related deaths and 64 gigatonnes (Gt) CO2-equivalent greenhouse gas (GHG) emissions that would have resulted from fossil fuel burning.""…nuclear power could prevent an additional 420,000 to 7.04 million deaths and 80 to 240 GtCO2-eq emissions due to fossil fuels, depending on which fuel it replaces."

@5:07 Nuclear energy is less than 5% of the total energy usage so I guess the police should chase the management of the oil/coal industry for killing 1.84 * 100 / 5 = 56.6 million people.Also, are the researchers sure that among those 1.84 million people there was not a single smoker? Smokers are not accounted among the Chrernobyl victims so they can't be counted as fossil electricity generation victims either. Same goes for people living in large cities where air pollution is caused by cars. Same goes for people living in Hawaii, where air quality is affected by volcanic gas emissions.

We offer private, commercial and personal loans with very low annual interest rates as low as 2% in one year to 50 years repayment period anywhere in the world. We offer loans ranging from $ 5000 to $ 100 million.

Our loans are well insured for maximum security is our priority. Are you losing sleep at night worrying how to get a legitimate loan lender? You bite your nails that fast? Instead of beating you, contact Paul William Home Loan (Loan Services) now, specialists who help stop loans bad credit history to find a solution that victory is our mission.

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

About This Site

Well, this was, until March 11, 2011. Now it is taken over by the events in Japan, first earthquake and tsunami but quickly by the nuke reactor accident. It continues to be a one-person (me) blog, and I haven't even managed to update the sidebars after 5 months... Thanks for coming, spread the word.------------------This is an aggregator site of blogs coming out of SKF (double-short financials ETF) message board at Yahoo.

Along with commentary on day's financial news, it also provides links to the sites with financial and economic news, market data, stock technical analysis, and other relevant information that could potentially affect the financial markets and beyond.

Disclaimer: None of the posts or links is meant to be a recommendation, advice or endorsement of any kind. The site is for information and entertainment purposes only.